The Flow of Glasses and Glass–Liquid Transition under Electron Irradiation

Abstract

Recent discovery and investigation of the flow of glasses under the electron beams of transmission electron microscopes raised the question of eventual occurrence of such type effects in the vitrified highly radioactive nuclear waste (HLW). In connection to this, we analyse here the flow of glasses and glass–liquid transition in conditions of continuous electron irradiation such as under the e-beam of transmission electron microscopes (TEM) utilising the configuron (broken chemical bond) concept and configuron percolation theory (CPT) methods. It is shown that in such conditions, the fluidity of glasses always increases with a substantial decrease in activation energy of flow at low temperatures and that the main parameter that controls this behaviour is the dose rate of absorbed radiation in the glass. It is revealed that at high dose rates, the temperature of glass–liquid transition sharply drops, and the glass is fully fluidised. Numerical estimations show that the dose rates of TEM e-beams where the silicate glasses were fluidised are many orders of magnitude higher compared to the dose rates characteristic for currently vitrified HLW.

On Crossover Temperatures of Viscous Flow Related to Structural Rearrangements in Liquids

“…Another crucial aspect of metallic systems operated in fast neutron reactors is the effect of radiation [ 1 , 2 ]. It is experimentally known that radiation affects the viscous flow; moreover, it significantly changes the character of viscosity, lowering the activation energy of the flow in condensed matter from the high value typical of glass to a low value, which is characteristic at high temperatures: E H → E L [ 74 , 75 , 76 ]. This results from the fact that irradiation breaks down interatomic bonds, thus facilitating the flow similarly to how the temperature does.…”

Thermal Effects and Glass Crystallization in Composite Matrices for Immobilization of the Rare-Earth Element–Minor Actinide Fraction of High-Level Radioactive Waste

“…To obtain monazite glassceramics, glass powder from lanthanum metaphosphate is mixed with an HLW simulant (oxides of Nd, Zr, La, Ce, Fe, Mo) and heated to 1200 • C, then cooled in a switched-off furnace, obtaining monazite and the ZrP 2 O 7 phase in the residual glass [84]. To suppress the formation of undesirable phases of ZrP 2 O 7 or FePO 4 , it was proposed to add B 2 O 3 or TiO 2 in the initial batch [148][149][150][151].…”

“…In another scenario, a container with HLW or SNF is placed into a pre-drilled hole filled with material with a lower melting point than the surrounding rocks [141][142][143][144][145][146], which facilitates their dipping. However, such proposals have not gone beyond theoretical calculations, which should also account for changes within the waste form [147,148].…”

NiTi2, a New Liquid Glass

“…[26], illustrates the positioning of liquid glasses in terms of connectivity and ordering increase (e.g., on temperature decrease). The connectivity between atomic species can be diminished not only by an increase of temperature: the irradiation of glasses, which breaks the interatomic chemical bonds, leads to fluidization of glasses [89].…”